Similar to what has been done on x86 & arm64, ok?
Index: conf/GENERIC
===================================================================
RCS file: /cvs/src/sys/arch/sparc64/conf/GENERIC,v
retrieving revision 1.316
diff -u -p -r1.316 GENERIC
--- conf/GENERIC 4 Feb 2021 16:25:39 -0000 1.316
+++ conf/GENERIC 23 Jun 2021 07:39:53 -0000
@@ -556,4 +556,5 @@ owtemp* at onewire? # Temperature
owctr* at onewire? # Counter device
pseudo-device hotplug 1 # devices hot plugging
+pseudo-device dt
pseudo-device wsmux 2 # mouse & keyboard multiplexor
